A Mount Carmel Cemetery visitor called police on Sunday morning to say the gravestones of three of his relatives had been toppled, police said in a statement. Officers found about 100 others knocked down. The incident apparently took place after dark on Saturday, police said.

ABC television affiliate WPVI said the damage was widespread and footage showed rows of headstones knocked down.

"I'm hoping it was maybe just some drunk kids. But the fact that there's so many, it leads one to think it could have been targeted," cemetery visitor Andrew Mallin, who had come to see his father's grave, told the station.

Vandalised tombstones at Mount Caramel CemeteryCredit:
AFP

The Anti-Defamation League, a watchdog group that monitors hate groups, is offering a $10,000 reward in the case, supported by the Mizel Family Foundation, police said.

The apparent vandalism came about a week after about 170 headstones were damaged at a Jewish cemetery in St Louis. Jewish community centers across the United States have also reported a surge in bomb threats, but all were hoaxes.

Muslim Americans have helped raise about $131,000 to repair the St. Louis cemetery, far exceeding organisers' $20,000 goal, according to their LaunchGood website.

Mr Trump delivered his first public condemnation of anti-Semitic incidents on Tuesday. The threats are "horrible and are painful and a very sad reminder of the work that still must be done to root out hate and prejudice and evil," he said.

The Anne Frank Center calls Trump's comments today "a Band-Aid on the cancer of Anti-Semitism that has infected his own Administration" pic.twitter.com/N29s6AXvv8

Some Jewish organizations have criticised his approach. The Anne Frank Centre for Mutual Respect in New York called his comments "a Band-Aid on the cancer of anti-Semitism that has infected his own administration."

Jewish groups had also criticized the White House for omitting any mention of Jews in its statement marking Holocaust Memorial Day last month.